A method and device for limiting power to protect power supply from overload in a multichannel audio amplifier

Abstract

A method for use in an audio system including a plurality of amplifier channels of corresponding audio channels. Each of the amplifier channels receives a respective input audio signal and is powered by a same power supply. The method comprises: obtaining a value of an indicator, wherein the indicator is representative of an energy reserve of the power supply; for each of the amplifier channels, determining a gain to be applied by an attenuation function to the respective input audio signal and a clipping level to be applied by a clipping function to the output of the attenuation function; wherein the gain decreases over time when the value of the indicator is below a threshold and the gain increases over time up to a maximum value when the value of the indicator is above the threshold, wherein the threshold is representative of a nominal energy level at which the power supply is in nominal operation; wherein the clipping level is determined as a monotonic function of the value the indicator.

1 . A device for use in an audio system including a plurality of amplifier channels of corresponding audio channels, each of the amplifier channels receiving a respective input audio signal and being powered by a same power supply, the device comprising processing circuitry for performing a method comprising,
 obtaining a value of an indicator, wherein the indicator is representative of an energy reserve of the power supply;   for each of the amplifier channels, determining a gain to be applied by an attenuation function to the respective input audio signal and a clipping level to be applied by a clipping function to the output of the attenuation function, wherein the gain decreases over time when the value of the indicator is below a threshold and the gain increases over time up to a maximum value when the value of the indicator is above the threshold, wherein the threshold is representative of a nominal energy level at which the power supply is in nominal operation; wherein the clipping level is determined as a monotonic function of the value of the indicator.   
     
     
         2 . The device according to  claim 1 , wherein the gain decreases over time by an attack rate. 
     
     
         3 . The device according to  claim 2 , wherein the attack rate is a fixed attack rate that corresponds to a fixed gain decrease per time period on a logarithmic scale. 
     
     
         4 . The device according to  claim 2 , wherein the attack rate is a dynamic attack rate computed as a function of the value of the indicator. 
     
     
         5 . The device according to  claim 1 , wherein the gain increases over time by a release rate. 
     
     
         6 . The device according to  claim 5 , wherein the release rate is a fixed release rate that corresponds to a fixed gain increase per time period on a logarithmic scale. 
     
     
         7 . The device according to  claim 1 , wherein, when the value of the indicator is below the threshold, the clipping level is determined by applying a monotonic function of an output voltage of the power supply. 
     
     
         8 . The device according to  claim 1 , wherein the monotonic function is a continuous function of the output voltage of the power supply. 
     
     
         9 . The device according to  claim 1 , wherein the indicator is proportional to the output voltage of the power supply or to the squared output voltage of the power supply. 
     
     
         10 . The device according to  claim 1 , wherein the indicator is proportional to the stored energy in the power supply. 
     
     
         11 . The device according to  claim 1 , wherein the gain varies between a minimum value and the maximum value. 
     
     
         12 . The device according to  claim 1 , wherein the monotonic function is adjusted based on mains voltage level signal received from the power supply. 
     
     
         13 . The device according to  claim 1 , wherein the processing circuitry comprises for each amplifier channel:
 a clipping circuitry connected to the input of the amplifier channel and configured to apply the clipping function;   an attenuation circuitry whose output is connected to the input of the clipping circuitry, wherein the attenuation circuitry is configured to apply the attenuation function.   
     
     
         14 . A method for use in an audio system including a plurality of amplifier channels of corresponding audio channels, each of the amplifier channels receiving a respective input audio signal and being powered by a same power supply, the method comprising,
 obtaining a value of an indicator, wherein the indicator is representative of an energy reserve of the power supply;   for each of the amplifier channels, determining a gain to be applied by an attenuation function to the respective input audio signal and a clipping level to be applied by a clipping function to the output of the attenuation function, wherein the gain decreases over time when the value of the indicator is below a threshold and the gain increases over time up to a maximum value when the value of the indicator is above the threshold, wherein the threshold is representative of a nominal energy level at which the power supply is in nominal operation; wherein the clipping level is determined as a monotonic function of the value of the indicator.   
     
     
         15 . A computer program comprising instructions that, when executed by at least one processor of a device of an audio system including a plurality of amplifier channels of corresponding audio channels, each of the amplifier channels receiving a respective input audio signal and being powered by a same power supply, causes the device to perform:
 obtaining a value of an indicator, wherein the indicator is representative of an energy reserve of the power supply;   for each of the amplifier channels, determining a gain to be applied by an attenuation function to the respective input audio signal and a clipping level to be applied by a clipping function to the output of the attenuation function, wherein the gain decreases over time when the value of the indicator is below a threshold and the gain increases over time up to a maximum value when the value of the indicator is above the threshold, wherein the threshold is representative of a nominal energy level at which the power supply is in nominal operation; wherein the clipping level is determined as a monotonic function of the value of the indicator.